The Leaves Are Cupping Up on My Dogwood

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The many graceful shapes of dogwoods (Cornus spp.) are known throughout U.S. Department of Agriculture plant hardiness zones 2 through 9, depending on species. These compact landscape plants are favorites of gardeners for their ease of care, but can develop cupping leaves in response to common troubles. Some species, such as the kousa dogwood (Cornus kousa; USDA hardiness zones 5 through 8), cup their leaves in response to adverse weather, but cupping leaves is a common problem for all dogwood species.

Powdery Mildew

If your dogwood's leaves were covered in a white, powdery substance before they began to fade to light green or yellow and cup, powdery mildew is likely the cause of your dogwood problem. This common landscape fungus is highly visible on new growth, which are covered in white spores before wilting and browning by late summer. Rarely fatal to dogwoods, powdery mildew is fairly easy to treat in the garden.

Powdery Mildew Control

Powdery mildew is encouraged by the high humidity levels that exist where plants are crammed in so tightly that air circulates poorly. Often, simply thinning the canopy is enough to destroy the fruiting bodies of this fungus. If you've opened the canopy and powdery mildew persists, try spraying your dogwood with neem oil concentrate, mixed at a rate of 2 tablespoons per gallon of water. Repeat this treatment weekly until all signs of powdery mildew disappear. Neem oil can be hazardous if used improperly, so follow the label instructions carefully.

Aphids

Aphids are tiny, sap-feeding insects that plague landscape plants. These small, variably colored pests huddle together on the undersides of leaves, sucking the juices directly out of their tender tissues. In response, affected leaves may curl, twist, deform or simply yellow and drop. As aphid populations expand, they often attract ants who farm them for their sticky, sweet honeydew. Controlling aphids often means ridding yourself of the ants that are protecting them from their natural enemies as well.

Aphid Control

Aphids are simple to control with daily sprays from a water hose. When you knock these slow-moving pests from the leaves where they're feeding, they can't reattach quickly enough to survive the journey back. Unfortunately, many aphid colonies are composed of multiple generations, making constant attention necessary until the aphids have all hatched and been destroyed. If ants are farming your aphids, apply a sticky barrier on a 4 inch-wide band of masking tape around the dogwood's main branches or trunk, 2 to 4 feet from the ground. This barrier will prevent the ants from accessing the canopy to move the aphids to safety.

Leaf Scorch

A variety of environmental stressors can cause an alarming curl -- known as leaf scorch -- in dogwood leaves. Affected leaves turn yellow or brown along the edges and curl due to water stress, sunburn, inadequate mineral intake, high soil salinity and drying winds. Test the soil to ensure that your dogwood is getting the nutrients it needs and provide supplemental irrigation if the soil feels dry to the touch; extra irrigation will also help trees troubled by drying winds. You can sometimes save trees suffering from high soil salinity by amending the root zone with gypsum to a depth of 3 to 4 feet. Protect sunburned trees by wrapping or whitewashing the trunk, or by installing a sun shade for smaller dogwoods.

About the Author

Kristi Waterworth started her writing career in 1995 as a journalist for a local newspaper. From there, her meandering career path led to a 9 1/2 year stint in the real estate industry. Since 2010, she's written on a wide range of personal finance topics. Waterworth received a Bachelor of Arts in American history from Columbia College.

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Waterworth, Kristi. "The Leaves Are Cupping Up on My Dogwood." Home Guides | SF Gate, http://homeguides.sfgate.com/leaves-cupping-up-dogwood-83762.html. Accessed 25 May 2019.

Waterworth, Kristi. (n.d.). The Leaves Are Cupping Up on My Dogwood. Home Guides | SF Gate. Retrieved from http://homeguides.sfgate.com/leaves-cupping-up-dogwood-83762.html

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